Clever way to jack up postal rates regularly without the usual public outrage.
The basis for this is the Postal Accountability and Enhancement Act, which keeps rate increases below inflation. The first forever stamps came out right after President Bush signed it, and this is the way the USPS can tie their fortunes to what they can charge. Many other countries have already gone this route.
It’s not so much a sign of the USPS but of the overall situation. But if you’d bought stamps with a set denomination, that amount would have been victim to inflation and more postage would have been required. You get a better deal now buying a first class stamp than you would have back in the 1970s—or by using old stamps on it (very expensive, as you lose all the inflation benefits).
With inflation adjustments, first-class letter postage is about 10-15% lower in cost than back then.